It is often helpful to determine the engine speed of internal combustion engines. Tachometers have been available for such purpose, such devices most commonly being employed to determine the speed of automobile engines; however, such devices can also be utilized to determine operational characteristics of such devices as powered lawn motors, portable RV generators, chain saws and the like.
Failure of internal combustion engines to operate properly can have harmful and undesirable consequences, not the least of which is the waste to gasoline, diesel, natural gas or other fossil fuels which occurs when internal combustion engines operate at less than peak performance. Furthermore, inefficient internal combustion engine operation can and does result in release of undue amounts of pollutants into the environment.
Hand held tachometers have been available in the marketplace for some time, but such devices are generally characterized by their bulk and lack of user friendliness. Most tachometers have been designed for use by professionals and on conventional ignition systems. This creates problems with regard to most new and modern electronic and computerized ignition systems. Improper hook-up or testing procedures can actually destroy a computerized ignition system and this can be very costly. For these reasons it is not feasible for many individuals to work on their own engines. This is aggravated by the fact that most small engines are designed without provisions for tachometer hook-up, or hook-up provisions are provided only for special tachometers.
The present invention relates generally to the field of inductive tachometers. While some relatively effective tachometers are known in the prior art, they are characterized by their relatively high expense, considerable bulk, and inability to be used in a variety of applications or in small or hard to reach places. Inductive pick-ups, by nature, have been fragile, prone to breakage, and expensive to repair.
U.S. Pat. No. 5,091,695, issued Feb. 25, 1992, discloses an electronic meter for determining engine speed in distributorless ignition system engines and conventional four stroke engines. The circuit disclosed in the patent was designed as a pulse to voltage converter to be employed with volt meters or multimeters on a millivolt scale.
The following patents are also believed to be representative of the state of the prior art: U.S. Pat. No. 3,601,773, issued Aug. 24, 1971, U.S. Pat. No. 3,811,089, issued May 14, 1974, U.S. Pat. No. 3,886,450, issued May 27, 1975, U.S. Pat. No. 3,963,987, issued Jun. 15, 1976, and U.S. Pat. No. 4,101,859, issued Jul. 18, 1978.